When, in the course of a pathological process or in predisposed individuals, the retina breaks, a retinal detachment may take place.
Retinal detachment is a disorder that inevitably led to blindness until 1918, when Tules Gonin proposed the ignipuncture treatment (puncturing and cauterizing) as a first effective treatment. Not only that, but, and perhaps more importantly, he introduced the conception that retinal detachment is cured when the occlusion of the tearing that created the detachment is achieved. In the 1950's, Charles Schepens proposes, as a means to achieve said occlusion, the placement of a circular explant that, sutured to the sclera, creates an indentation in the area corresponding to the tear. That same decade, a method for definitive sealing was proposed. The method comprises the creation of local inflammation in both the retina and the choroids surrounding the tear, this leading, eventually, to an adherence stronger than the physiological one. In order to achieve that adherence, Meyer-Schwickerath proposed the use of photocoagulation. A decade later, Lincoff achieved the same effect utilizing localized cold, by means of the method known as cryopexy. In 1971, Robert Machemer and Golham Peyman, each one of them working separately, publish the first works using vitrectomy to repair detached retinas. Said methodology consists of tackling a retina from inside, entering the eye through the pars plana and extracting the vitreous that is tractioning the retina. This permitted the advent of the utilization of internal tamponading to replace the vitreous, such as silicone oil (originally disclosed by Cibis in 1962, but whose use extended with vitrectomy); the exchange of fluid by gas (Steve Charles, 1977) and perfluorocarbon (Stanley Chang, 1987). These have been the fundamental advances in retinal detachment surgery and, up until today, have been the pillars for the treatment of that problem.
Internal tamponades are used to position and maintain the retina applied against the eye inner wall, when a retinal tear caused the detachment.
The way to achieve a permanent adherence between the detached retina and the pigment epithelium (PE) wall is to provoke a localized inflammation by means of a laser beam or another thermal source. The inflammation creates an adherence between retina and PE that is much stronger than the physiological adherence. However, said adherence can only be achieved by maintaining both parts in contact in the course of a process that may last several days before consolidation. Because of that, the use of tamponades is necessary.
Preferably, tamponades are used temporarily. Liquid perfluorocarbon is a heavy and transparent liquid used during surgery and has to be removed before the surgery is finished.
Silicone oil, with various densities, may be left inside the eye for periods of weeks or even months. It is introduced during one surgical operation and is extracted with another ad hoc operation,
Air was the first element used when fluid was exchanged by gas. However, air remains inside the eye for 48 hours only, this time being insufficient to permit a definitive attachment of a retina to its eye wall. Consequently, gas tamponades with special gases having longer reabsorption periods are used.
Gas tamponades are based on the use of gas formulations (for example, C3FS and SFS in variable dilutions) permitting that the gas bubble maintain a useful volume inside the eye for a long time (time ranging from few days to several weeks).
Both gas tamponades and silicone oil act by pushing a retina upwards by flotation, within the eye liquid medium. It is because of this that in those cases where retinal injuries that need to be pushed are not placed at an upper location, patients are compelled to maintain and unnatural position for several days. This obvious discomfort for a patient may create work disability and, frequently, major musculoskeletal sequels, all of this provided the patient strictly abides to his positioning, what is being achieved in less than 50% of the cases; thus the procedure success rate being reduced. Because of the same reason, when the injuries are inferior, only in some cases an aberrant position achieves therapeutic usefulness. For the remaining cases with inferior injuries, internal tamponades are not effective. There exist composite silicone oils having a density higher than water's that permit the tamponading of inferior injuries, but leave uncovered upper injuries.
When they get into contact with crystalline posterior capsule, both gas tampons and silicone oil firstly create a posterior capsule opacification and then, a cataract, this making necessary new surgery to replace the crystalline few weeks or months later.
The use of these tamponades may lead to a partial vision loss or even to glaucoma blindness. In the specific case of gas tampons it is difficult to predict their expansion capacity, which varies according to the diverse concentrations and different individuals.
Thus, a sudden and excessive expansion of a gas tamponade may rapidly take intraocular pressure to values higher than the pressure of the arteries supplying the retina and the optic nerve, this leading to tissue death by an ischemia of those structures.
Although the use of oils may create a sudden pressure increase with an ensuing risk of blindness by the blocking of the internal circulation of fluid, it also takes place a pressure increase due to the blocking of aqueous humor outflow by oil bubbles in the Schlemm's canal.
In some patients, silicone oil creates corneal degeneration, because of which a transplant is required as a sole possible way to recuperate a useful vision.
Lastly, a characteristic common to both tamponading forms is the visual disability created while the tamponade remains in the eye. In the case of gas tamponades, these disappear by themselves within a period of 2 to 6 weeks, time during which vision is extremely impaired by the use of the tamponade. On the other hand, in the case of oil its use is not recommended for more than 6 months, during which vision may be extremely impaired. This not only impacts on the work life of treated patients, but on their social life as well. By the same token, beyond this period oil complications (such as the creation of cataracts and glaucoma) are very frequent.
The prolonged use of intraocular oil has shown that oil ends up infiltrating the inner layers of the retina, this having unknown effects on its functioning.
To store silicone oil longer than two months may bring about its emulsfication: this consists of the formation of very small bubbles starting from the large oil bubble. These small bubbles agglomerate and form a white-colored level, similar in aspect to foam, that interfere with vision completely if they reach the visual axis.
On the other hand, another important limitation of gas tamponades is the impossibility of traveling on an airplane, since the sudden expansion created by the atmospheric pressure drop may lead to blindness before the patient descends to sea level.
An additional disadvantage to the utilization of silicone oil tamponades is that in pseudophakic patients, that is to say those patients with intraocular lenses, oil attaches to the lenses surfaces and remains there even after it is extracted. Thus, said oil bubbles may definitely alter the lens optical quality and, consequently, patient's sight.
In the previous art we find the US patent application 2005/0203333 A1, where it is disclosed the utilization of magnetic nanoparticles for the treatment of retinal detachment: “Magnetized scleral buckle, polymerizing magnetic polymers and other magnetic manipulations in living tissue”. In particular, in said document it is disclosed the use of magnetic nanoparticles in a medium that polymerizes inside the eye, creating a compact solid that is then attracted by a permanent magnet with a specific shape of a 360° ring (scleral buckle). According to said disclosure, the fluid, once polymerized inside the eye, gets its definitive shape. It is because of this that once the scleral buckle is removed, the polymer persists in the inside without adapting to the eye wall profile. If for any reason the polymer happened to be not effective and the retina detached again, the polymer would remain inside the eye as a foreign body, what would hinder a subsequent surgical operation. ocular.